Dental implants have always been a subject for study and researches. In recent years the medical world has been investing a lot of effort to improve dental implants. The straight-forward implant insertion procedure cannot be implemented when the edentulous alveolar ridge bone is insufficient, either in quality or quantity, (For example, fresh extraction sites, especially of multi-rooted or ankilosed teeth, that require more resection of bone to be accomplished). Furthermore, the high complication rates accompanying those cases, due to the anatomical proximity of the alveolar nerve or the maxillary sinus, poor bone quality and incorrect three-dimensional relation to the opposite dentition or ridge, are all important parameters in treatment plan considerations. Such cases are typically defined as sub-optimal alveolar ridge for implant insertion.
Under the conditions mentioned above (and others), augmentation of the future implantation site is necessary for long-term successes. This is done mostly by Guided Bone Regeneration (hereinafter “GBR”), using autogenic or allogenic bone grafting and/or allopllastic bone-substitute grafting and a biological barrier (membrane). The membrane is used for inhibition of connective-tissue proliferation into the grafted site thus, thereby creating better conditions for osteoinduction and osteoconduction by the grafting material.
The surgical procedure for GBR is technique-sensitive, and the failure rate and complication rate are considerably higher, comparing to the “simple” implant insertion procedure. Even when done by a specialist, the GBR procedure is still a time consuming procedure and thus very expensive for the patient. The surgical part of the treatment is usually divided into two or three sessions and lasts for several months. Some cases would require even more treatments due to arising complications.
By the conventional protocol of the GBR procedure of implanting a dental implant, after local anesthesia, the surgeon exposes the edentulous alveolar crestal bone at the future implant site. Granulation tissue is removed to prepare the bone defect to be grafted. Then autogenic bone harvested from other site. In the alternative, allograft bone/alloplast grafting material is prepared and applied to the defect. After designing the desired ridge contour, the graft is covered by membrane. When necessary, bone pins or screws are used to avoid migration of the bone particles or the membrane over the newly-shaped ridge. The flap has to be deliberately released by means of wide reflection, releasing cuts and periosteal scoring in order to cover the augmented alveolar crest without any tension. Failure to achieve this, results in the most common cause for the aforementioned complications (dehiscence, infection of the graft and failure to achieve the required quality and quantity of alveolar bone formation). Basically, the major difficulty lies with covering an enlarged volume of augmented bone with the same amount of soft tissue.
A second technical difficulty is the insertion of the dental implant at the same stage, since the ridge is not solid, but rather composed of a moist powder and small particles of bone or substitute. It neither can hold nor can be arranged properly around the implant and still be covered by the membrane and the mucoperiosteal flap. Mainly due to this reason, only after four to nine months, (once the bone graft is consolidated and replacement resorption by natural host bone cells occurs to some extent) a second intervention is performed. In this stage, after local anesthesia and second exposure of the bone by flap reflection, serial drills into the newly reconstructed ridge are followed by the insertion of the dental implant. Next, the flap is sutured over the implant and an additional healing period of three to six months is usually required.
After the latter healing period, a third surgical intervention is needed for the implant head exposure and the connection of a trans-mucosal part as a healing cup, which is than replaced after few weeks by a prosthetic platform for restoration of the tooth. This stage requires local anesthesia and sutures, as well. Hence a total of three surgeries and three appointments for suture removal are usually needed while carrying out the conventional procedure.
Nowadays, most dental implants are made of Titanium and are shaped as a cylinder or a screw. Bone grafting materials are commercially available in various forms and consistencies as allografts or alloplasts delivered as block, powder, grains, putty or gel. Some of the materials require preparation or manipulation during surgery, rendering them exposed to the non-sterile environment of the dental clinic and to an increased contamination risk. Delivery of the grafted material is usually done by dental spatula or special syringe which is neither accurate nor efficient.
Polypeptide growth factors are recombinant biologic mediators that regulate cellular activity. They include growth factors (e.g. PDGF, TGF-β, igf-1, vegf and the like), differentiation factors (e.g. BMP-2, OP-1, GDF-5, GDF-7), matrix factors (such as fibronectin, vitronectin, thrombobospondin-1) and platelets-rich plasma (“PRP”). Recent studies demonstrated induction of bone growth by rhBMP-2, carried by injectable collagen or semisolid calcium-phosphate cement, in craniofacial and dentoalveolar defect in animals model and human.
Recently, commercially available rhBMP-2 (Induct-os®, INFUSE®) and op-1® putty were approved for clinical use by the FDA, Some of them for maxillofacial application.
Another crucial part of the above-described procedure is the GBR membranes, which are available as sheath or mesh of absorbable (collagen) or non-absorbable material (such as PTFE or Titanium). The membrane has to be molded in the three-dimensional form of the augmented ridge and the adjacent implants or teeth. This time consuming process is carried out by trial and error during the operation. Another fact that makes working with the GBR membrane even more difficult is that most of the absorbable membranes, when become wet, turn out to be softer and more difficult for manipulation. In certain cases the membrane has to be fixated to the surrounding bone by mean of miniature pins or screws to avoid graft mobility and leakage. Again, the exposure time of the grafted area and the membrane during these trials affect the total operation time, and increase the chances of post operative infection as well as other complications.
Several methods and implants using bone grafting techniques are known in the art, for example U.S. Pat. No. 6,722,884 discloses a method for preserving the alveolar ridge surrounding a presently extracted root socket by backfilling the socket with bone grafting material and installing an implant in the root socket area. As described in this publication, the dental implant may be installed apically into the root socket immediately following root extraction. The open area of the root socket surrounding the implant is then backfilled with bone grafting material immediately after the implant placement. In the alternative, the presently extracted root socket is filled with bone grafting material, the bone-growth is promoted in the root socket by the bone grafting material for 2-12 months. Then, after sufficient bone growth has been promoted, an implant is installed in the extraction site area in the normal manner.
Another publication that relates to bone grafting technique is US 20060008773 which describes a titanium-mesh umbrella for bone grafting used to combine with conventional implant and to hold bone grafting material in proper position during dental implant placement procedure. The titanium-mesh umbrella forms a projecting umbrella surface with a curvature in perpendicular direction. After the titanium metal umbrella has been positioned a guide tissue membrane can than be securely attached and a space for bone growth can be maintained.
However, there is still a need for an implant and a procedure for using it that is less time consuming and consequently would reduce the costs associated therewith would lower the complications rate.